Desmid
of the month
October 2005

Xanthidium
antilopaeum

The genus Xanthidium is characterized by biradiate cells furnished with a
series of spines along the outer margin. Usually, the semicell centre
is more or less inflated and sculptured by granules or large scrobicles.

The most
common species of this genus is X. antilopaeum. It is marked by
hexagonal semicells the apical and lateral angles of which as a rule are
furnished with two stout spines each.

Quite a
number of varieties have been described, mutually differing in the disposition
of the marginal spines and the central pattern of scrobiculae. Some of
those varieties are that different from the nominate variety that they
might be considered species of their own.

Of the
varieties herewith represented, the nominate variety (var. antilopaeum)
in the Netherlands is of rather common occurrence in various mesotrophic,
slightly acidic to slightly alkaline water bodies whereas var. planum appears to be confined to acidic moorland pools and var. laeve is predominantly encountered in oligotrophic quaking bog hollows.